Image forming apparatuses each have a plurality of rotary bodies such as a photoconductor and developing roller. Most of the apparatuses also include a plurality of motors for rotating the rotation bodies respectively. For instance, during activation by power-on, some of inactive motors need to be activated individually and controlled to rotate at respective required rotation speeds. However, during motor activation, a larger amount of electric current generally has to be supplied as compared with an electric current needed under fixed speed control. To activate the plurality of motors at the same time, the apparatus needs to include a relatively high-capacity power supply.
To avoid the need for the high-capacity power supply, conventionally, for start-up of a plurality of motors, they would be activated in order at different timings. A first motor is first activated and, after a lapse of a predetermined activation time from the activation start thereof, a second motor is activated. After a lapse of an activation time of the second motor, furthermore, the first and second motors are judged to be in a controllable state. As this activation time, for example, a maximum time required for activation of the relevant motor is set.
This case however may cause a disadvantage that a wait time is long from power-on until image formation becomes ready to start. On the other hand, there is disclosed an image forming apparatus in which the activation timing of a motor of which the start-up characteristic is stable during activation, such as a pulse motor, is set without any time interval from the activation timings of other motors (e.g., see Patent Literature 1).